1. Field of the Invention
The present invention relates to a heart pulse wave detecting device for detecting the peak points and the base points of a heart pulse wave when the heart pulse wave is measured, which the device is adaptable for hemadynamometers, blood flow rate measuring device, pulse oximeters, pulse-wave velocity measuring device, and the like.
2. Related Art
An auscultatory method and an oscillometric method are known for the blood pressure measuring methods employed for the blood pressure measuring device. The auscultatory method has the following disadvantages. It is sensitive to noise. The sounds within the body tend to be left out. Sometimes the sounds are left even below the diastolic blood pressure.
In a blood pressure measurement by the oscillometric method which can solve the problem of degrading the blood pressure measuring accuracy, a pulse wave signal representative of a pulsation in an artery is detected in the form of a variation of a pressure in a cuff, and a systolic blood pressure and a diastolic blood pressure are measured on the basis of the pressure variation.
In the blood pressure measurement by the oscillometric method, the systolic blood pressure and the diastolic blood pressure are measured on the basis of a variation of the amplitudes of a heart pulse wave signal. For this reason, the peak points and the base points of a heart pulse wave are measured. In this case, the peak points of the pulse wave are detected for the amplitudes thereof, and a variation of an slope of the pulse wave is detected for the base points of the pulse wave.
The peak points of a heart pulse wave distinctly appears in the waveform. Accordingly, it is easy to reliably detect the peak points. The base points of the heart pulse wave are points where the slope of the waveform is changed in the direction. Because of this, it is difficult to detect the base points.
Particularly, when the cuff pressure transiently fluctuates, drifts, and suffers from noise during the decreasing process of the cuff pressure, problems arisen from such transient variations of the cuff pressure are additionally contained in the waveform data to be computed. This results in exacerbation of the accuracy of specifying the base points, and exacerbation of the accuracy of measuring the systolic blood pressure and the diastolic blood pressure.